Comparison of Two Methods for Extracting Site-specific Soil Environmental Background Data from Soil Pollution Investigation Data

Site-specific soil environmental background values play a significant role in soil environmental management in China. Soil environmental background values can be extracted indirectly from site soil pollution investigation data. In the study, two indirect methods, the robust normal probability Q-Q plot method and the standard threshold method, were applied to both the research case data and simulated data, and the effectiveness and applicability of the two methods were compared and analyzed. The soil cobalt (Co) content data from the research case study site exhibited a bimodal distribution pattern, originated from two distinct populations. The simulated data, M₁ and M₂, are composed of background data (B) and non-background data (N₁ or N₂). M₁ is composed of B and N₁, with more overlap between them, while M₂ is composed of B and N₂, with less overlap between them. The results indicate that, for the research case data, the difference between the soil environmental background data separated using the robust normal Q-Q plot method and the standard threshold method are minimal, and they exhibit similar statistical characteristics to those obtained using the background reference area method. For the simulated data, both the standard threshold method and the robust normal Q-Q plot method effectively separated the soil environmental background data from simulated data M₁ and M₂, which closely resemble the statistical characteristics of B and the influence of different degrees of overlap in the simulated data on separating background data is minor. However, the background data separated by the standard threshold method which is simple and easy to operate are closer to B, so the standard threshold method is more suitable for the separation of soil environmental background data. This study provides methodological insights for the obtaining of site-specific soil environmental background data.